Thermostat housing is the bit with all the pipes coming out of it on the right of the engine (your "right" when you stand infront of the car looking at the engine i.e. passenger side)
look at a smaller diameter black rubber hose coming from this side of the engine which turns downwards and then goes rearwards towards the enginecompartment/passenger compartment bulkhead. Just as the pipe leaves the thermostat house there is a small black plastic wheel which you unscrew a bit to release trapped air.
Do the bleeding process initially with the engine off and the coolant bottle cap removed.
Did you already drain your coolant? Why? If you were changing it you should have flushed it out aswell, by pouring gallons of clean water into the coolant expansion bottle. You should also have done this with the heater set to HOT and started the car for a few minutes before starting the coolant draining procedure. And during "flushing" ensuring that most of the water being flushed is coming out of the bottom of the rad.
Personally I prefer to remove the rad top hose where it enters the thermostat housing, for the flushing procedure.
Then you have to fill it up again, use undiluted antifreeze 2.5 - 3 lters, then top up with clean water.